Trimethylamine oxide respiration in Proteus sp. strain NTHC153: electron transfer-dependent phosphorylation and L-serine transport

Cells of Proteus sp. strains NTHC153 grown anaerobically with glucose and trimethylamine oxide (TMAO) were converted to spheroplasts by the penicillin method. The spheroplasts were lysed by osmotic shock, and the membrane vesicles were purified by sucrose gradient centrifugation. Vesicles energized electron transfer from formate to TMAO displayed active anaerobic transport of serine. An anaerobic cell-free extract of Proteus sp. disrupted in a French pressure cell reduced TMAO with formate and NADH with the concomitant formation of organic phosphate. The net P/2e- ratios determined were 0.1 and 0.3, respectively. The NADH- and TMAO-dependent phosphorylation was sensitive to uncouplers of oxidative phosphorylation (protonophores), and the formate- and TMAO-dependent serine transport was sensitive to ionophores and protonophores. We conclude that TMAO reduction in Proteus sp. fulfills the essential features of anaerobic respiration.